Process of coating metals



Nov. 3, 1931. F. R. GLENNER PROCESS OF COATING METALS Filed July 6. 1929WW n m l m INVENTOR ran 51's Richard Glenn E! I A TTORNE Y Patented Nov.3, 1931 PATENT OFFICE FRANCIS RIC HARD GLENNER, OF BROOKLYN, NEW YORKrnoonss on COATING METALS Application filed July 6, 1929. Serial No.876,393.

The present invention relates to the covering or coating of ametallicvsurface with another metal.

With metallic pipes, boilers; pans and other vessels coated with aprotective covering or coating of another metal by processes heretoforeknown, difiiculty has been ex perienced in preventing the separation ofthe covering metal from covered surfaces when the same is subjected toheat, torque or vacuum and under various other influences. The pipes,vessels andother utensils, therefore, soon deteriorate and are rendereduseless, in addition to vitiating the product being treated in-suchvessels.

An object of the invention is to provide a process whereby a coveringmetal may be united with a metallic surface so as to insure adherence ofthe metals together in an inseparable bond under all conditions ofstrain, torque, vacuum influences, pressure, vibrations and heat up tothe melting point of the covering metal.

A' further object of the invention is to so apply the covering metal tothe surface to be covered as to provide in the application of the metala covering of uniform thickness and homogeneity, free from air pockets,pin holes, or other faults in the construction thereof, and without thenecessity of subsequent shaping or leveling after the covering has beenapplied.

Further objects of the invention are simplicity of process andapparatus, facility and economy in operation, and certainty of the finalproduct.

The process consists briefly in applying the coating metal to themetallic surface to be coated in a molten state and in a reducingatmosphere.

This process may be carried out by the employment of certain apparatusfor confinin the coating metal in contact withthe surface to be coated,and providing means for introducing a volatile reducing agent betweenthe surface to be coated between a wall of said. apparatus and thesurface to be coated. While the process is especially applicable in the.uniting of a covering of lead to an iron base, its'use is contemplatedin the/prescut application in the covering of any given metallic surfacewith anothermetal or alloy 7 whose melting point is sufficiently belowthat as meaning that the process is applicable 7 only as related tothese metals.

I have found that lead and other metals suitable for covering purposesmay be made to adhere tenaciously to the surfaces of their bases byapplying them to the foll9wii1g- I process, and that such covering willnot be dislodged from the base under any of the ordinary stresses orinfluences to which they may be subjected as torque, bending, vacuum,pressure, vibration or temperature up to the melting point 'of thecovering metal.

' In applying my process to the coating of steel or cast-iron with lead,the surfaceof the iron or steel to be covered or coated is firstthoroughly cleaned so as to free it from scale, rust, dirt and otherobjectionable substances. This cleaning may be accomplished by theapplicationof either a sand blast or one of the well known p'ckIingagents, or by the successive application of both.

Suitable pickling agents are hydro-fluoric acid, HF; nitric acid, HNOhydro-chloric acid, HCl; sulphuric acid, H SO applied at a range oftemperatures varying from 100 to 160 F. according to the metal inquestion and the acid to be used.

The concentration of these pickling agents may vary, also, according tothe acid and to the metal treated between 10% and 50%.

The particular acid used may be varied I with the metal to be treated asfor instance,-

hydro-fiuoric acid is found to be particularly effective in the picklingof silicon iron, especially when used in' a concentration of about 30%.Hydrochloric acid is quite effective when applied to chrome steelat aconcentration of between 20 and 50% while nitric acid has particularapplication to the pickling-of copper and brass in a dilute solution ofabout 10%. A 20% solution of sulfuric acid may be effectively used inthe pickling of usual varieties of iron and steel.

After the pickling operation the acid is washed off and the metal to becoated may be subjected to a fluxing. treatment and to a preheating aswill presently be more fully set forth. Both of these steps are optionaland may be used or omitted as occasion or convenience may dictate.

' Where fluxing is desired suitable fluxing agents are ammonium chlorideNH Cl or zinc chloride Zn'CI Antimony chloride SbCl may also beeffectively used and other suitable chlorides varying with conditions.

The concentration and temperature of the fiuxing salts are important intheir application to the metallic surface to be coated, working bestaround the concentration point of the particular salt used, although thework is also effective in a weak solution and over a range up to thesaturation point; the temperature of the solution should be around 160F. for most eifective results.

After the flux has been applied to the metallic surface to be coated,the same may be preheated to the melting point of metal to be used as acoating or covering agent. This step may be resorted to as a matter ofeconomy in time and when resorted to, may take place in an enclosedfurnace or otherwise, as desired.

The metallic coating or covering is next applied to the cleaned surfaceof the metal and this may be done in any suitable manner, as by pouringor dipping; the coating metal being, of course, in a molten state. Thecoating metal may be effectively applied in a reducing atmosphere as ofpure, dry hydrogen.

The lead used is preferably in a pure chemical state or, where a hardlead surface is desired, an antimony lead may be used, that is, leadcontaining antimony over a range up to about 10% beginning with afraction of one per cent. l

The covering may be effectively applied in an enclosure having 'asurface or wall spaced from the surface to be covered a distance equalto the thickness of the covering or coating desired. The casing andother apparatusused in connection, with the coating is preferably madeof a high temperature alloy, or chrome steel or chrome-nickel steel, assuch alloys are least effected by temperature changes. The molten leadmay be introduced into the enclosure between these surfaces, the articleto be coated being maintained the while at thetemperature of moltenlead. This may be accomplished by submerging the enclosure in a bath ofmolten lead maintained in a molten condition in any well known manner.

The preliminary heating of the article to be coated may take place inthis bath but to save time it may be preheated in a furnace, as setforth above.

Excellent results are obtained by applying the covering or coating in areducingatmos phere suitably introduced into the enclosure along withthe molten lead, hydrogen being,

an excellent medium for this purpose.

Preliminary to the introduction of lead into the enclosure, anatmosphere of hydrogen may be passed through the enclosure until testsshow that all air has been driven out. The application of the moltenlead at auniform temperature throughout the mass in an enclosure and inan atmosphere of hydrogen with provision for escape of the air and othergases relieves the lead of occluded air and other impurities and insureshomogeneity of structure for the covering while the application withinthe enclosure, as set forth above, insures uniformity of thickness.-

In the accompanying drawings is illustrated apparatus for covering apipe with a metallic layer.

In the drawings Figure 1 is a longitudinal section through the apparatusand,

Figure 2 is a closure cap for the enclosure for the pipe.

This apparatus comprises a tubular enclosure or casin 10 in which thepipe 11 to be covered, in t e present instance on its outer surface, issuitably supported in coaxial spaced relation to the inner wall of thecasing, as by gauges 12 which may be separably or integrally formed withclosure caps 13 for the ends of the casing. These caps may be providedwith central openings 13 to allow free flow of the molten metal of thebath through the pipe being coated, thusmaintaining more uniformtemperature. A

The inner surface as well as the outer surface of' the enclosure 10 areuntreated by either the'sand blast or pickling processes described aboveand are left in' an uncleaned condition in order to prevent adhesion ofcovering metal thereto. The pipe 11 on the other hand is cleaned by oneor both of these methods before being mounted in the casing. Thethickness of the gauge used will correspond to the thickness of coveringdesired on the pipe 11 and the casing must also be selected of asuitable diameter with this end i a pipe 17- is provided communicatingwith the conduit for supplying a reducing agent into the casingsimultaneously with the 11101- ten metal forreducing any oxides that maybe contained therein, causing the reducing agent to start'flojvmg priorto the admission of the molten inetaland stopping the [low of thereducin agent prior to the cutting off of the flow 0 molten metal. Theflow of reducing fluid through this pipe is controlled by valve 18. Thepipe also serves for the introduction of hydrogen preliminary to theintroduction of the molten metal for driving out air and other gases.

To this end an outlet pipe 19 for the gas is provided communicating withthe conduit 20 leading from the casing 10 to a balancing cup 21. The pie 19 is controlled by a valve 22 and the con uit 20 by the valve 23.

It will be noted by reference to the drawings that the balancing cup 15is of considerably greater capacity than the cup 21 and that its bottomis on a level. with the top of,

cup 21. By this arrangement pouring of the molten metal is facilitatedand the pouring may be continued until the metal overflows the on 21. Afurther function-of these cups with t eir conduits extending in avertical direction fromthe enclosure is to insure the escape of alloccluded air and other gases in the molten coating mass.

The molten metal and the pipe to be covered should be maintained atuniform temperature throughout the mass until the pouring is completed,a suitable temperature being that of the molten metal; A convenientmanner of accomplishingthis is to submerge the casing the while in abath of molten metal 24 of the same character as the coating or coveringmetal.

This bath is contained in a receptacle 25 which may be heated in anysuitable manner, as by gas burners controlled by valves 26.

In carrying out the process in this apparatus, the bath 24'is firstbrought to a molten state, the reducing fluid, as hydrogen, is caused topass through the casing 10 by opening valves 18 and 22 until a testshows the interiorof the casing-to be free from air.

It will be noted thatthe conduits 14 and 20 communicate with the space27 between the pipe tobe coated and the casing at the extreme endsthereof in order to provide a flow of reducing hydrogen the entirelength of the surface to be coated, thus preventing.

air pockets or regions untreated by the reducing agent. P s v The space27 having been freed of air, the valves 16 and 23 are opened and moltenmetal allowed to flow into the space 27 completely filling the same andoverflowing cup 21 into the bath 24, the valve 22 the while being closedand the valve 18 open until near the end of the flow of the moltenmetal. When the space 27 is so filled and the height of the molten metalis the same on both sides, i. e..

balance each other, and the operator is satisfied that the reducingagent has acted sufliciently to give the desired result, thelvalves 16and 23 maybe shut oflf and the casing 10 removed from the bathandallowed to cool.

With the surface of the pipe treated as above, a bond will beformed-between this surface and the covering metal inseparable underordinary conditions of torque, vacuum influence, severe vibrations,pressure or heat up to the melting point of the covering metal.

The coating obtained is non-porous, free from pin holes or gas pockets,and'a homogeneous unionof the two metals is provided.

The process also has the advantage of sun- .plieity, economy andapplicability to the process by adapting the apparatus to the specificconditionsto be dealt with.

I claim i v 1. The process of casting one metal upon the surface ofanother, consisting in cleaning the surface of the base metal to receivethe cast, enclosing the base metal within a cham ber defining theelected cast, raising the tem perature of all to the melting point ofthe casting metal by submersi'on in a bath of the casting metal inmolten condition, educting the oxygen from the chamber, pouring thecasting metal in molten form into the chamher along with nonoxidizinggas to exclude 2. The processof casting one metal upon the surface ofanother, consisting in cleaning the surface of the base metal,positioning the base metal in a mold, heating the base metal and mold toapproximately the melting point of the casting metal, and applying thecasting metal to the basemetal in molten form together with a permeationof nonoxidizing gas.

3. The process of casting one metal, upon the surface of another,consisting in cleaning the surface of the base metal, positioning thebase metal body in a mold spaced fromthe base metal by a chamberdefining the cast to be made, heating the base metal-and mold toapproximately the melting point of the casting metal, and applying thecasting metal to the base metal by introducing into the mold in moltenform together with a permeation of non-oxidizing gas.

In testimony whereof I have signed my name to this specification.

FRANCIS RICHARD GLENNER.

. oxygen in the pouring and cooling the cast.

